Effect of serotonin infusions on the mean plasma concentrations of growth hormone, thyroid hormones and the amount and constituents of milk in the Sanan goat

The goal of this study was to determine whether serotonin increase the mean plasma concentrations of thyroxine (T4), triiodothyronine (T3), growth hormone (GH), milk amount and constituents in the Sanan goats. Nine Sanan goats were randomly divided into 3 groups. Each group received daily infusion of 1, 4 or 8 ng serotonin agonist (hydroxytryptophan) (5HT) for 7 days. Blood and milk samples were collected daily on day 1 before infusions until 3 days after the last infusion. Samples were assayed for plasma T3, T4 and GH concentrations by double-antibody RIA. Milk samples were assayed for protein, fat and lactose constituents. The daily amounts of milk were determined throughout the experiment. Infusions of 1 ng 5HT did not change the plasma concentrations of the T3, T4 and GH throughout the experiment period. Infusions of 4 and 8 ng 5HT significantly (p<0.01) increased the plasma concentration of the T3, T4 and GH among animals. Infusions of 1and 4 ng 5HT did not change the amount and the protein, fat and lactose constituents of milk among all animals in the different groups. 8 ng 5HT significantly (p<0.01) increased milk amount from 0.6 to 1.2 liter on the 10th day of experiment. Infusions of 8 ng 5HT did not change the protein, fat and lactose constituents of milk. The result of these experiments indicated that serotonin may increase the mean plasma concentration of GH, T3, T4 in the Sanan goats.